Free Rev Boost #'s????

2psi?!? How am I supposed to know, the first mark on the gauge is at 10psi, and the needle doesn't move w/o a load.
 
at 3200 rpm I can hit 11psi with my twin setup, but that is punching it from 2000RPM. Are you saying that yours holds continuous boost free revving?

Lavon
 
LAmiller said:
at 3200 rpm I can hit 11psi with my twin setup, but that is punching it from 2000RPM. Are you saying that yours holds continuous boost free revving?

Lavon
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Yeah It's from a slow steady rev and holding it at 4k it will make and maintain 25psi, And im not sure how it can possible build that much with no load on the engine, I had issues trying to load the video last nite, I'll try again tonite.

And im not saying anything about it being better or worse as in a performance manner, but find it rather odd since in my other previous trucks and everyone else dosent find results like that at all.

Brett
 
Tcolesanti said:
Ding ding ding.................... we have a winner!!!!!!:hehe:

-Tom
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Do I win the magical 500hp key? LOL

Only way I can see turbos building boost while free revving is the fact that they are getting spun up higher than normal at idle and as we all know, the faster a turbo spins the more boost it's going to make. Now why it varies wildly between trucks, who knows, but that's the reason I come up with. Now one thing I have noticed is that if I slowly ease up the rpm's to redline it won't make boost but if I just floor it and let it rap up real quick it'll build boost.
 
@ 3000 RPM continuous, I have 7 psi in the manifold, and 3 psi in the cold pipe.

HX40/16 over GT42-02/1.15 A/R

Helix 2 cam and mild head porting
 
dzlfarmboy said:
Yeah It's from a slow steady rev and holding it at 4k it will make and maintain 25psi, And im not sure how it can possible build that much with no load on the engine, I had issues trying to load the video last nite, I'll try again tonite.

And im not saying anything about it being better or worse as in a performance manner, but find it rather odd since in my other previous trucks and everyone else dosent find results like that at all.

Brett
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...seems like a cam timing issue?
 
dzlfarmboy said:
Yeah It's from a slow steady rev and holding it at 4k it will make and maintain 25psi, And im not sure how it can possible build that much with no load on the engine, I had issues trying to load the video last nite, I'll try again tonite.

And im not saying anything about it being better or worse as in a performance manner, but find it rather odd since in my other previous trucks and everyone else dosent find results like that at all.

Brett
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Have you checked the timing? I was getting 30psi@ 3000rpm in park with a HX35/16cm. I checked my timing and it had slipped to 11 or 12 degrees, I put it back to 20* and the boost in park dropped to about 5psi.
 
BrettWINspeed said:
Have you checked the timing? I was getting 30psi@ 3000rpm in park with a HX35/16cm. I checked my timing and it had slipped to 11 or 12 degrees, I put it back to 20* and the boost in park dropped to about 5psi.
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It was set at 18* to seat the o-rings first, so Im free tonite and will retorque the head one last time and I'll pin the pump and check it to make sure its still at 18* for now. Cant imagine it sliped much if any it seems to run good on the street for just normal driving.

Brett
 
So, what's wrong with boost on a free rev? I suppose when under a load the lack of timing is not very productive.

It be nice to have 20PSI on a launch with a manual tranny and not slip the clutch. :)
 
with my SPS62 @ 3000 = 5 psi.....4000= 10-11 psi
Silver Bullet @ 3000 = 0......4000 = 5 psi
 
How many people actually went outside to check this?

I will just stick to breakin stuff while the truck is actually in gear.
 
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